Classes are templates
that can be used
to create objects.
An object created using a class
is known as an instance
of that class.
A class is created
as shown in the example below:
In the example given above,
we defined a class User.
Inside the code block
of the User class,
there is a function constructor.
The constructor function is invoked
whenever a class instance is created,
as shown in the example given below:
In the example given above:
-
We created an instance admin
of the User class
using the new keyword.
-
Whenever new User() is executed,
the constructor function of User
will be invoked.
The arguments passed inside
the parentheses in new User(),
get passed to the constructor function
inside the User class.
-
Inside the constructor function
of the User class,
we first display
"This is from the constructor"
using console.log
to demonstrate that the
constructor function is invoked
whenever new User() is executed.
-
Then we assign the value of
the name parameter to this.name
and
we assign the value of
the age parameter to this.age.
What this does is,
it creates the properties
name and age in the instance
that was created.
Hence the value "Sam Smith" gets
assigned to admin.name
and
the value 32 gets
assigned to admin.age.